The present invention relates to improved copper base spinodal alloys which are characterized by good strength properties as well as good ductility and to an improved process for their preparation from powder.
Copper, nickel and tin spinodal alloys have received significant attention in recent years as a potential substitute for copper-beryllium and phosphorbronze alloys in applications which require good electrical conductivity in combination with good mechanical strength and ductility. Heretofore, the major thrust of commercial production of coppeer base spinodal alloys has been through conventional wrought processing. Typical wrought processing is disclosed in U.S. Pat. Nos. 3,937,638, 4,052,204, 4,090,890 and 4,260,432, all in the name of J. T. Plewes. The processing involves preparing a copper-nickel-tin melt of desired composition and casting the melt into an ingot by conventional gravity type casting techniques such as DC casting and Durville casting. The cast ingot is then homogenized and thereafter cold worked in an attempt to break up the cored structure which results during the casting. The material is then worked to final dimensions, annealed, quenched and aged, generally with cold working between the quenching and aging. Attention is directed to U.S. Pat. No. 3,937,638 which describes the foregoing processing in detail.
While copper base spinodal alloys have been successfully prepared on a laboratory scale by the processing outlined above, the process has never proved to be commercially viable for a number of reasons. As a result of the conventional casting technique employed, the final product is characterized by tin segregation, generally at the grain boundaries, which has a detrimental effect on its strength and ductility. This tin segregation is directly attributable to the coring which occurs during casting. While a degree of the tin segregation can be eliminated by cold working, annealing and quenching the as-cast material, these operations increase the overall cost of the final product to the point of making the material noncompetitive with those materials it is intended to replace.
A roll-compacted copper-nickel-tin alloy prepared from a powdered mixture of the three metals is described by V. K. Sorokin in Metalloved. Term. Obrab. Met., No. 5, pages 59-60 (1978). The product from the disclosed process, however, possesses only moderate strength and poor ductility.
It is naturally high desirable to provide copper base spinodal alloys characterized by good strength properties in combination with good ductility which are convenient to process and may be made economically on a commercial scale.
Accordingly, it is a primary object of the present invention to obtain such alloys and to provide such a process for their preparation.
It is a further object of the present invention to provide a process as aforesaid for obtaining copper base spinodal alloys characterized by a microstructure which is substantially free of tin segregation.
Further objects and advantages of the present invention will appear hereinbelow.